Injection molding



P 2, 19475 T. F. STACY INJECTION MOLDING 2 Sheets-Sheet 1 Original F11 3 March 16, 1943 75 I 1 Q WW 7/ INVENTOR 4 Fflfagy ATTORNEYS Sept. 2, 1947. I T. F. STACY 2,426,651

' INJECTIQN MOLDING Original filed uarch 16. 1943 2 Sheets-Sheet 2 INVENTOR BY' v ATTORNEYS Patented Sept. 2, 1947 INJECTION MOLDING Thomas F. Stacy, Piqua,

French Oil Mill Ohio Ohio, assignor to The Machinery Company, Piqua,

Substitute for abandonedapplication Serial No.

479,355, March 16, 1943.

This application March 4, 1946, Serial No. 651,749

6 Claims.

This application is a substitute for abandoned application Serial No. 479,355, filed March 16, 1943.

This invention relates to the molding of resinous materials, and more particularly to materials of the type which harden following the addition thereto of a hardening agent. The thermosetting resins are excellent examples of this type of material, which may be fluids or solids at ordinary temperatures. Such resins when in fluid form or when reduced to fluid form by heating may be molded easily by injection molding. One difficulty with the injection molding of such mate rials is that such resins should have an added agent to accelerate hardening and thus reduce the time required for hardening, and if such materials with added agent are reduced to liquid form by heat, and stored they tend to polymerize or harden rather rapidly, before they can be used. Hence it has been customary to reduce such resins with agent to fluid form only during the molding operation and as a part thereof.

In the copending application of Thomas F. Stacy and Max D. Farmer, Serial No. 418,640, filed November 12, 1941, there is disclosed and claimed an invention in injection molding of thermosetting resinous materials in which the accelerating or hardening agent is incorporated in withdrawn increments of the resinous material while the latter is in liquid or fluid condition, and before it reaches its final position in the mold cavity. It is highly important that the hardening rate be as rapid as possible after the material is injected into the mold cavity (usually heated), and this invention is in the nature of an improvement upon the invention disclosed in said copending application, in that it relates to a method and apparatus for obtaining more rapid and uniform hardening of the resinous materials disclosed in said application after they reach the mold cavity.

An object of this invention is to provide an improved method and apparatus by which resinous materials may be molded by injection into mold cavities and hardened to self-shape-retaining form in a minimum of time; which will require a minimum of modification of prior methods and apparatus for injection molding; with which the amount of hardening agent required may be kept to a minimum; with which the time required for a molding operation may be reduced to a minimum; and which will be relatively simple, practical and inexpensive.

Other objects and advantages of the invention will be apparent from the following description 2 of several embodiments and examples of the invention, and the novel features will be particularly pointed out hereinafter in connection with the appended claims.

In the accompanying drawings:

Fig. 1 is a sectional elevation through a portion of a two-part mold constructed in accordance with this invention, with the injection nozzle shown in section and applied to the mold;

Fig. 2 is a sectional elevation of the same, approximately along the line 22 of Fig. 1, so as to show one example of the groove or passage between the sprue and the mold cavity;

Fig. 3 is a sectional elevation, similar to Fig. 2, but illustrating another embodiment of the invention differing from those of Figs. 1 and 2 in the manner in which the passage formed by the groove is given repeated and substantial changes in direction of progress;

Fig. 4 is another sectional elevation similar to Figs. 2 and 3, but illustrating still another embodiment of the invention,by showing another typeof groove or passage for connecting the sprue and the mold cavity;

Fig. 5 is a sectional elevation, similar to Fig. 1,

but illustrating the groove as formed in the section having the mold cavity instead of in the section having the sprue;

Fig. 6 is a sectional elevation of a portion of the mold of any of the examples of Figs. 1 to 5, or of other examples, in which the passage is formed by aligned grooves in both of the abutting faces of the mold sections in a manner to form an undulato-ry passage;

Fig. 7 is a sectional elevation of a portion of one section of the die, and similar to Figs. 2 to 4, but illustrating another type of groove for causing eddying of the stream passing between the sprue and the mold cavity;

Fig. 8 is a transverse, sectional elevation of the same, with the section taken approximately along the line 8-8 of Fig. 7

Fig. 9 is a longitudinal sectional elevation through apparatus for delivering the resin and catalyst in measured and proportional quantities under pressure;

Fig. 10 is a transverse sectional elevation through a portion of the same, the sectionbeing taken approximately along the line 1 61 0 of Fig. 9; and

Fig. 11 is another sectional elevation of a portion of the same, the section being taken approximately along the line H-Il of Fig. 9.

In the embodiment of the invention illustrated in Figs. 1 and 2, the mold is made up of a plurality of abutting sections, two of such sections and H being shown in this particular example, although it will be understood that any number of abutting sections may be used in order to provide a desired multi-part mold. In one of these sections, such as all), the mold cavity 12 is formed of the desired shape and size, with one side or wall of the cavity formed by the abutting face of another section such as II, which may have, if desired, a projection I la thereon extending into the mold cavity formed in the first section Ill. The section II is also provided with a tapered sprue 13 by which the resinous material to be molded may be admitted in fluid form to the cavity l2, and in accordance with this invention, the sprue I3 is disposed iaterally toone side of and spaced from the cavity H. The sprue 13 is usually formed in the section which does not contain the mold cavity [2, and such a spru'e'may be divergentin a direction towards the opposing faces between the sections, or toward the mold cavfty, as usual in injection iholding apparatus.

The Clitorfid "ofthe spine 13 a concave seat M which receives the convex end or an injection nozzle I 5, tnroughwhicn the iiuid resinous material -to he -molded discharged under pressure to the shrue l3. suitable injection nozzle t5 inay' be employed-and it is separable the seat 14hr the mold between molding operations when desired, as is understo'od in this-art. Such a-noazle l5 and delivery-mechanisrn may, for co ienceoe of the type shown in said prior Stacy a d-Farmer'application, herei-nabove iden tified, 61- it may be formed in any other suitabl ,soas to discharge into the semenua to be molded anda propo tional qeantrty of a hardening agent.

The race of the mold section 1- which abuts the section I0 is provided with a channel or growers wl-i ioh is generally somewhat spiral or to udils and-o ens he and into the'spr-ue 1'3 s eaths-other ien'd into one 'mold cavity 12-. This groove 1 6 is closed alling it's open face by the abutting face of thesection 10,50 that it provides a confined passage c'on-necting the sprue F3 and the rid-61d bavity fl through which the resinous material and hardening agent-must passin reaching the mold cavity. This passage is decidedly tortuous with substantial changes in direction of progress so that-the -s'trea rn of molding resin and hardening agent passing to the mold cavity from t fsprue will be subjected to sufiicient agitation and eddying that will 'c e a thorough mixing of the hardening agent and "esin before the two reach the mold cavity 12. Any suitable way of obtaining such a tortuous passage or changes in direction of traveler the-confined stream of resin and hardening agent m y be employed, that shown in Fig. 2 being 'a generally spiral form with straight sections corinected'by angular sections orturns of about QOdegrees. 7

In Fig. 3, the adjacent stretches of thepassage connected by angular turns 'of more than 90 'degrees "provide a figure somewhat resembling a spiral triangle, 'the angular *c'hange's being more abrupt that in Fig. 2. InFig. 4, a still different type oftortuous passageissnownfor thegroove I6. 7

Figs. 7 and 8 illustrate how the straight stretches of the passage or groove can be further modified tojrorm a tortuous passage Hi and'cause eddy'ingjor mixing ."of the contents of the stream .passingalong "the same. Inft'h'is instance, {the groove 16 isjfo'rmedby milling shallow cylindrical cavities 16a, in the face of the section II, so that the groove provided in the opposite faces.

the cavities intersect one another, with islands or pins IT in the centers of the cylindrical cavities so as to divide the stream and thereby cause additional agitation or eddying of the stream. This arrangement with islands, as shown in Figs. 7 and 8, may be employed in any of the sections of the groove I 6 shown in Figs. 1 to 5.

Obviously, any portion of the groove or passage l6, and particularly the straight sections thereof, may be further formed to increase the eddying or agitation of the stream. For example, the grooves may be formed partly in each of the abutting races between two sections, by milling cylindrical convex cavitie l8 in aligned portions of the abutting faces, as shown in Fig. 6, so as to form hills emd valleys in the portions of Each valley should be approximately aligned with a hill of the corresponding part of the groove in the other section. In this manner, the passage will undulate back and forth in directions across the plane of the abutting faces between the sections, and the fluid, resinous material in passing from the spr-ue l3 to the cavity l2, as it moves along this undulatory passage, will be caused to move back and forth and extent, which will thoroughly mix the hardening agent with the'resinous material.

In Figs. 1 to 4, the groove entirely in the mold section having the sprue l3 and with which the injection nozzle i5 is engaged and disengaged, so that when one desires tolmold articles of a difierent shape or configuration, the same section ll with groove 16 may be employed with another section Ill having a different .mold cavity, and it is only necessary to change the section Ill which carries the mold cavity. This makes it unnecessary to form the tortuous groove when making each mold cavity, since to same section 'Il may be used with a plurality of different sections Ill having different mold cavities therein. However, in Fig. 5, .I have illustrated an example in which the groove 1 6 is formed entirely in the section lt havingthe mold cavity 12 therein. It will also be understood that the groove may be iormed partly inone av d partly in "theother sectiongii' des-i-red, sparticularlywhen one desires to use the' imdulatory arrangement of .Fig. 6. c Siniil-arlyjthe type of groove shown in Figs. 7 and 8 may be formed entirely in one mold -section alone, or partly in one and partly in the other. For example; the. islands H may be formed on onesection'suchas i0, and'the cylin- 11 cal cavit'ies 01' recesses tor-med iin' the-other sect-i as ll. Obviously, other modifications and com intuition of these features may be em- {ployedin order to meet particular problems :ofiniteration molding, and ito' give the desired degree 'g'of the iresinous irraterialiand the hardm g agent before the mixture reaches its'final "removed and the mold used for the manuiacture of additional as ."I his sustained "s desirable in order to keep thernold V I i ed, until the material in the mold cavity harden sufifi-oiently lto retain its or iginaisnape. i

The resinous material and the hardening agent maybe any or those whichharden ifrom a fluid "condition following the addition thereto or: a

eddy to a substantial 1'6 is shown as formed hardening agent." Such "materials and agents are available inthe market. Those preferred are the thermosetting resins, suchas' the phenolaldehyde condensation resins-which advance from an intermediate stage, -in .which they may be rendered'fluid by heat, to'a final solid stage by' polymerization that is accelerated by the addition thereto of a, catalyst or accelerating agent, such as hexamethylenetetramine. Other examples are set forth in said copending .appli cation hereinbefore identified. The walls of the groove -l6 and the sprue are,'of-course, given a slight divergence toward the parting face between the sections was to facilitate .removal .of the mixture that 'hardens'in the'sprue and in thegroove l6. w l

Any suitable mechanism :may be: employed for delivering the mixture' of catalyst and resin to be molded, into the 1 mold and Lone/example of such mechanism, as disclosed in said Stacy and Farmer application, is shown. in Figs. 9 to 11. This delivery mechanism includesa base 20. havingan upstanding portion 2l containing a relatively'large cylinder or chamber 22 and a relatively small cylinder or chamber '23. A piston 24 fits andreciprocates in'the cylinder 22, anda pistonv 25. fits and reciprocates in a cylinder 23. The piston 24 extends into a chamber 26 and therein carries a piston head 21. .Pipes 28 and 29, suitably controlled, admit operating fluid under pressure alternately to opposite ends of the chamber 26, so as. to cause reciprocation's of the piston 24. The piston 24 carries, rack teeth 38 which mesh with, and drive, a pinion 3| in a shaft 32 which is rotatably supported in a'bearing 33 carried by' an upright standard 34 of the base. Aplate 35 is confined on the standard 34 for vertical, reciprocat'ory, sliding movement thereon, -and it carries a .rack bar 36 which mesheswith the pinion 3|. The pinion is long enough to mesh with'teeth 30 of the piston Y24 and also-.with the verticallyrmoving rack 'bar 36. As the piston 24 reciprocates it moves the plate 35 upwardly and downwardly. v Hinged to this plate at His 2; guide. 38 with its other end providedwith a clamp bolt 38a which moves in an arcuate slot 39 that'has a center of curvature at 31, is releasably secured in difierent adjusted positions along the slot 39 to place guide 38 in selected angular positions on plate 35. A roller 40 which runs in a channel of the guide 38 is fixed on one end of a stub shaft 4| (Fig. 11) that is rotatably mounted in the small piston 25, and this shaft at its end opposite the roller 40 also carries a roller 42 which runs in a slot 43 provided in a bracket bearing 44. The plate 35 moves vertically at the same time that the piston -24 is moving endwise, and the channel member 38 thereon will have a cam action on the roller 40 and through it move the smaller piston 25 endwise and in the same direction, but proportionately through a distance depending upon the angular position of the guide 38' on the plate 35. The small cylinder 23 at its forward end opens into a small, long, tubular nozzle 45 which extends into and along an ofiset passage 46 forming a continuation of the larger cylinder 22. The end of the nozzle 45 terminates approximately at the end of the offset passage 46. A small, ball check valve 41 is provided in the passage between the cylinder 23 and the nozzle 45, so as to pass fluid from the cylinder 23 into the passage of the nozzle 45 but seat automatically to prevent reverse flow. A reservoir 48, secured to the upper part of 6 theupright 2|; hasa passage 49 openingdowm Wardly therefrom into. the forward end of the cylinder123 and carries a .ball .check valve .50 which opens to pass fluid from the reservoir 48 to the vchamber'23. Valve 50 is spring operated into closed position automaticallyto prevent .reverse flow- Similarlyareservoir 5|, also provided on the upper part, of the upright 2|, has a passage'52; leading .to cylinder 22. The forward end of the upright 2|, carries a removable nozzle I5 which, forms a continuation of the passage 46, and through it thenozzle 45 extends. Whenthev pistons 24 and 2 5 are retracted, increments of fluids willbe drawn from the reservoirs 48 and}! into-thecylinder 23'and "22 respectively, and thatwhen the pistons 24 and 25 are advanced, these increments of fluid will be deliveredsimultaneously into the mold at the-exit endof the, nozzle J5, all as explained in greater detail in said Stacy andFarmer application.

I It will be understood that various changes in the details, materialsand arrangements of parts, which have been herein described and illustrated in order to explain the nature of theinvention, may be made by those skilled in the art within the principle and scope of the invention,.as expressed in the appended claims. v r I claim as my invention: 7 1. The method of injection molding of a resinous material of a type which may harden to a solid object following the addition thereto of a hardening agent, which comprises storing a quantity of said'material in fluid condition, withdraw ing said material in increments, injecting said withdrawn increments under a substantial pressure differential into a closed cavity of a mold, until the cavity is entirely filled with said mate rial, addingto said increments before their injection into said cavity, anon-gaseous agent which causes a material acceleration of the hardening of said material, conducting the mixture of agent and material as a confined stream in its passage to said cavity, causing repeated and substantial eddying and mixing of said agent and materials in their travel to said cavity, and holding said mixture in said cavity under suflicient pressure to keep the cavity entirely filled untilthe contents of said cavity. harden to a self-.shape-retaining body.

2. The method of injection molding of a resinous material of a type which may harden to a solid object following the addition thereto of a hardening agent, which comprises storing a quantity of said material in fluid condition, withdrawing said material in increments, injecting said withdrawn increments under a substantial pressure difierential into a closed cavity of a mold, until the cavity is entirely filled with said material, adding to said increments before their injection into said cavity, a non-gaseous agent which causes a material acceleration of the hardening of said material, conducting the mixture of agent and material as a confined stream in its passage to said cavity, causing repeated and substantial tortuous travel of said stream throughout the major part of its travel to said cavity, whereby the contents of the stream will be mixed by the eddying in the stream caused by such tortuous travel, and holding said material in said cavity under sufficient pressure to keep the cavity entirely filled until the contents of the cavity harden to a self-shape-retaining body.

3. The method of injection molding of a, resinous material of a type which may harden to a solid object following the addition thereto of a hardening agent, comprises storing a quantityof said mater "1influidcondition,with-- drawing said material n increments, injecting said withdrawn increments under a substantial pressure difierential into va closedcavity of a moldnntil the cavity is entirely filled with solid material, addingto :saidiincrements before their injection into said cavity, a non-gaseous agent which :causesa material acceleration of the hard-I ening of said material, conducting the mixture of agent and material as aconfinedstream in its passage to said cavity, causing repeated and sub stantial' undulatory travel of said stream' in a direction crosswise of the general direction of progress of said stream to 'said cavity and in directions toward and from the -f ace between the sections sufiiciently to cause a thorough mixing off'the agent and materials duringtheir travel toward said cavity, and holding said mixture in said cavity under sufiicient pressure to keep the cavity'entirely filled until the contents of said cavity harden to a self-shape-retaining body.

"4; Apparatus for'injection molding of resinous material of a type whichhardens to a solid follow ing the addition thereto of a hardening agent, which comprises a 'multi-section mold having a mold cavity opening into the abutting facesbetween sections, and a sprue extending from the space between abutting faces of the sections outwardly and terminating in an outwardly facing seat,

a nozzle device removablyfitting said seat, and means for delivering concurrently through said nozzle into said sprue, streams of said resinous material and hardening agent in fluid form, said mold having therein and exposed at a face between abutting sections, a tortuous passage with frequent abrupt changes of direction of progress connecting said mold cavity and said sprue, whereby the mixture in reaching said cavity'f-ro-m said nozzle device will be thoroughly mixed, and when the sections are separated, said tortuous passage will be uncovered for cleaning throughout its entire length.

5. Apparatus for injection molding of resinous material of a type which hardens to a solid following the addition thereto of a hardening agent, which comprises a multi-section mold having a mold cavity opening into the abutting races between sections and a sprue extending from the space hetweenabutting faces of the sections outwardly and terminating in an outwardly racing seat, a nozzle device removahiy fitting said seat,-, and meansyior delivering concurrently through said nozzle into said sprue, streams of said resinous material and. hardening agent in vfluid term, said mold having a passage connecting said cavity :and said sprue constituting a groove along the abuttingiaces of said sections, opposed walls of said'groove formed by 'said sections bein undulated in a direction toward and from the, general plane of the face between the abutting sections, with the hills inone-section disposed opposite the valleysv in the opposed wall of the groove, whereby when the mixture of resin and hardening agent is discharged into said sprue and conducted therefrom through said passage to said cavity, the mixture will pass a confined stream throughsai'd passageand be turned back and iorth within the passage and caused to thoroughly-mix before reaching said cavity.

.6... Apparatus for injection molding "of resinous material of a type which hardens to a solid following the addition thereto of a hardening agent, which comprisesa multi se'ction mold, one of said sections having a mold-cavity therein which is closed on one side by the abutting 'face of the other :section,'said other section having a sprue connecting. the exterior face thereof to the abutting faces of said sections at a substantial distance across said abutting faces from-said cavity, the outer end of said sprue being surrounded with :a, seat to receive the complementary end of a nozzle through which a mixture of a resinous material and a hardening agent may be discharged :into the sprue, a passage connecting said sprue/and said cavity and formed entirely as a groove in that face of said other section which abuts said one section, "but closed hy said one section, said passage having a plurality of substantial changes in direction to produce a tortuous course as it'progresses from said sprue to said cavity, whereby the fluid discharged into the sprue and passing to said cavity will be agitated sufliciently to cause a-s'ubstantial mixing of the agent and resinous material before it reaches said cavity; I

' THOMAS P. STACY. 

